Nice portraits thanks , fa 77mm or fa 43mm looks nice I will check it out more samples online.

OK the K-1 the FA 43 is a normal lens like the old 50mm on 35mm film. It's a little short for most people - unless you like to get really close to the subjects. I like the DA 40 on crop - a lot like shooting 58mm on film but going to say the FA 31 on crop is like shooting the FA 43 on FF - it isn't my favorite focal length for portraits. It can be done - but it has you working very close and requires more work on lighting to avoid being in between the light and your subject. Of the two the FA 77 seems a better choice on FF albeit a ilttle shorter than some may like. With your exisitng 70-200, when you do portraits what focal length do you prefer? (For distance to subject, subject perspective, etc. )

The FA 77 f1.8 gives a very good working distance. Note that, as an FA lens, it does not have Quick Shift, so manual focus tweaking when in Auto Focus must be done by flipping the camera to manual focus. Or just use manual focus all the way. This is not really a problem for portraits, which is not timing sensitive.

Depends on how much of people you want to include in the picture and how much blur you want. I use FA* 85/1.4, 100/1.5 @f2,2 (special projection-type lens for infrared portraits), 85/1,4 soft focus DIY lens, 140/1,8 projection lens or 141/1,9 projection lens for half and full body portraits, and 168/1,9 or 178/1,9 projection lenses for full height portraits. The best range for me in aspect of blur / communication with model ratio is 135-150 mm on FF camera.

In regards of lenses I prefer for portrait manual focus when working with adults but for kids you got to have auto focus. I used a lot when I was shooting professionally Zeiss lenses, as they have very nice micro contrast.
Now that I just doing it as a hobby anything fast with above mentioned focal lengths will do.

My mostly used lenses now are Sigma 35mm 1.4, Sigma 50mm 1.4 and Sigma 70mm 2.8 and some old manual focus primes in 135mm and 200mm.

In regards of lenses I prefer for portrait manual focus when working with adults but for kids you got to have auto focus. I used a lot when I was shooting professionally Zeiss lenses, as they have very nice micro contrast.
Now that I just doing it as a hobby anything fast with above mentioned focal lengths will do.

My mostly used lenses now are Sigma 35mm 1.4, Sigma 50mm 1.4 and Sigma 70mm 2.8 and some old manual focus primes in 135mm and 200mm.

I have never used any sigma lenses but I heard some sigma lenses has af issues on k1 ,do u have any problem with using sigma lenses on pentax camera?